Q3 A student used a laser, as illustrated in Fig 14.30, to demonstrate that light is a wave motion. (i) Name the two phenomena that occur when the light passes through the pair of narrow slits. (ii) A pattern is formed on the screen. Explain how the pattern is formed.
(iii) What is the effect on the pattern when: (a) the wavelength of the light is increased (b) the distance between the slits is increased.
(iv) Describe how the set-up in Fig 14.30 could be used to calculate the wavelength of the light from the laser.
(v) The other approach taken to calculate the wavelength of light is with the use of the spectrometer. Describe the function of each of the labelled parts of the spectrometer in Fig 14.31.
(vi) The ‘laser method’ and ‘spectrometer method’ both demonstrate that light is a wave motion, but does not indicate if it is transverse or longitudinal. Describe an experiment to demonstrate that light waves are transverse waves.
(vii) Give a practical use of Polaroid material. Screen Telescope (6) (12)
HALF QUESTION Typical of Question 12 in Leaving Cert. Exam
Q4 Answer both of the following parts (a) and (b). (a) Sunlight is made up of different colours and invisible radiations.The different colours of the spectrum can be demonstrated by dispersion.
(i) What is meant by the underlined terms? (ii) Name the two types of radiations that are closest in wavelength to visible light. 256 INVESTIGATING PHYSICS
